U.S. patent number 8,278,240 [Application Number 12/596,935] was granted by the patent office on 2012-10-02 for method of production of transition metal nanoparticles.
This patent grant is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Fanny Barde, Alexander Talyzin, Kyoichi Tange.
United States Patent |
8,278,240 |
Tange , et al. |
October 2, 2012 |
Method of production of transition metal nanoparticles
Abstract
There is provided a method of stably producing nanoparticles of
a metal alone, in particular a transition metal alone, the method
comprises heating a chelate complex (M-DMG) comprised of two
dimethyl glyoxime (DMG) molecules and one transition metal (M) ion
at 300 to 400.degree. C. so as to generate transition metal (M)
nanoparticles carried on carbon particles. The method preferably
comprises heating a mixture of said chelate complex (M-DMG) and
alumina so as to generate transition metal (M) nanoparticles
carried on alumina. Preferably, the transition metal (M) is one of
Ni, Cu, Pd, and Pt. Typically, the generated transition metal (M)
nanoparticles have a size of a diameter of 5 to 15 nm.
Inventors: |
Tange; Kyoichi (Susono,
JP), Talyzin; Alexander (Umea, SE), Barde;
Fanny (Zarenten, BE) |
Assignee: |
Toyota Jidosha Kabushiki Kaisha
(Toyota-shi, Aichi-ken, JP)
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Family
ID: |
39467231 |
Appl.
No.: |
12/596,935 |
Filed: |
February 28, 2008 |
PCT
Filed: |
February 28, 2008 |
PCT No.: |
PCT/JP2008/054098 |
371(c)(1),(2),(4) Date: |
February 12, 2010 |
PCT
Pub. No.: |
WO2008/132881 |
PCT
Pub. Date: |
November 06, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100152041 A1 |
Jun 17, 2010 |
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Foreign Application Priority Data
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Apr 24, 2007 [JP] |
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2007-114392 |
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Current U.S.
Class: |
502/167; 502/185;
502/331; 977/773; 502/335; 502/184; 502/337; 502/332; 502/333;
977/810; 977/775; 502/406; 502/339; 502/334 |
Current CPC
Class: |
C01B
3/0026 (20130101); B22F 9/30 (20130101); B01J
23/72 (20130101); B82Y 30/00 (20130101); B22F
1/0018 (20130101); B01J 23/40 (20130101); B01J
37/086 (20130101); B01J 23/755 (20130101); Y02E
60/327 (20130101); Y02E 60/32 (20130101); B01J
35/006 (20130101) |
Current International
Class: |
B01J
31/00 (20060101); B01J 23/72 (20060101); B01J
23/56 (20060101); B01J 23/44 (20060101); B01J
20/02 (20060101); B01J 23/40 (20060101); B01J
23/00 (20060101); B01J 21/18 (20060101); B01J
23/74 (20060101); B01J 23/42 (20060101) |
Field of
Search: |
;502/184,185,331-335,337,339,406,167 ;977/773,775,810 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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11-157835 |
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Jun 1999 |
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JP |
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2001-192712 |
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Jul 2001 |
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JP |
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2004-168641 |
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Jun 2004 |
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JP |
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WO 03/061827 |
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Jul 2003 |
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WO |
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Other References
"Synthesis and characteristics of NiO nanoparticles by thermal
decomposition of nickel dimethylglyoximate rods," Xueliang Li et
al. Solid State Communications 137 (2006), pp. 581-584. cited by
examiner .
X. Ni et al., "Synthesis of Nickel Nanocrystallites with Hexagonal
Flake-like Morphology from Nickel Dimethylglyoximate," Chemistry
Letters, vol. 33, No. 12, pp. 1564-1565 (2004). cited by
other.
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Primary Examiner: Hailey; Patricia L
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, LLP
Claims
The invention claimed is:
1. A method of production of transition metal nanoparticles,
comprising: heating a chelate complex comprised of two dimethyl
glyoxime molecules and one transition metal ion at 320 to
380.degree. C. so as to generate transition metal nanoparticles
carried on carbon particles.
2. A method of production of transition metal nanoparticles as set
forth in claim 1 wherein said transition metal is one of Ni, Cu,
Pd, and Pt.
3. A method of production of transition metal nanoparticles as set
forth in claim 1, wherein the generated transition metal
nanoparticles have a size of a diameter of 5 to 15 nm.
4. A method of production of transition metal nanoparticles,
comprising: heating a mixture of a chelate complex comprised of two
dimethyl glyoxime molecules and one transition metal ion and
alumina at 320 to 380.degree. C. so as to generate transition metal
nanoparticles carried on the alumina.
5. A method of production of transition metal nanoparticles as set
forth in claim 4, wherein said transition metal is one of Ni, Cu,
Pd, and Pt.
6. A method of production of transition metal nanoparticles as set
forth in claim 4, wherein the generated transition metal
nanoparticles have a size of a diameter of 5 to 15 nm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a national phase application of International
Application No. PCT/JP2008/054098, filed Feb. 28, 2008, and claims
the priority of Japanese Application No. 2007-114392, filed Apr.
24, 2007, the contents of both of which are incorporated herein by
reference.
TECHNICAL FIELD
The present invention relates to a method of production of metal
nanoparticles, more particularly a method of production of
transition metal nanoparticles.
BACKGROUND ART
"Metal nanoparticles" are typically fine particles of a sole metal
of a diameter of 5 to 15 nm or so. Compared with the conventional
particles of diameters of the order of several .mu.m or more, they
have an overwhelmingly larger specific surface area and thereby an
extremely large activity, so are promising for diverse applications
such as a material for storage of hydrogen or other gases. In
particular, transition metal nanoparticles are promising for
diverse areas due to their high chemical activity.
However, for example, as proposed in Japanese Patent Publication
(A) No. 2004-168641, various ways are known for producing
nanoparticles of metal oxides, but metals, in particular transition
metals, alone have an extremely high chemical and physical
activity, so end up easily forming compounds or aggregates. It was
extremely difficult to stably produce nanoparticles.
DISCLOSURE OF THE INVENTION
The present invention has as its object the provision of a method
for stably producing nanoparticles of a metal alone, in particular
a transition metal alone.
Means for Solving the Problem
To achieve the above object, the present invention provides a
method of production of transition metal nanoparticles
characterized by heating a chelate complex comprised of two
dimethyl glyoxime molecules and one transition metal ion at 300 to
400.degree. C. so as to generate transition metal nanoparticles
carried on carbon particles.
If heating a chelate complex (M-DMG) comprising two dimethyl
glyoxime (DMG) molecules and one transition metal (M) ion at a
temperature of a prescribed range, nanoparticles of the metal M
along released from the M-DMG are obtained in a state stably
carried on the particles of C similarly released.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows TEM photographs of Ni nanoparticles generated in a
state carried on amorphous carbon by the present invention using
Ni-DMG alone as a starting material. (1) is a high magnification
photograph of an area surrounded by the square in the field of
(2).
FIG. 2 shows a TEM photograph of Ni nanoparticles generated in a
state carried on alumina by the present invention using a mixture
of Ni-DMG and alumina as a starting material.
FIG. 3 shows a graph showing the relationship of the specific
surface area and heating temperature of Ni nanoparticles generated
by a heating temperature inside and outside the prescribed range of
the present invention.
FIG. 4 shows a graph showing the relationship of the pressure and
hydrogen storage amount at room temperature for Ni nanoparticles
generated by the method of the present invention from Ni-DMG alone
or an Ni-DMG/alumina mixture and a conventional bulk Ni.
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the chelate complex (M-DMG) comprised of
two dimethyl glyoxime (DMG) molecules and one transition metal (M)
ion as a starting material has the structure of the following
formula 1.
##STR00001##
By heating M-DMG in the temperature range of 300 to 400.degree. C.,
nanoparticles of the metal M alone released by the decomposition of
the M-DMG are generated in a state carried on C alone. If the
heating temperature is less than 300.degree. C., the above reaction
will not occur, while conversely if the heating temperature is over
400.degree. C., the generated particles will remarkably agglomerate
and nanoparticles will not be able to be obtained. Here, the reason
why the metal M and the carbon C are generated in an independent
state without oxidation is believed to be that the H released due
to decomposition of the M-DMG forms a reducing atmosphere.
According to a preferred embodiment of the present invention, by
heating a mixture of the chelate complex M-DMG and alumina at the
temperature of the prescribed range, nanoparticles of the metal M
alone with a higher specific surface area are obtained in the state
carried on alumina particles.
According to a preferred embodiment of the present invention, the
transition metal M of the chelate complex M-DMG is any of Ni, Cu,
Pd, or Pt.
The transition metal nanoparticles generated by the method of the
present invention have a size of typically a diameter of 5 to 15
nm.
EXAMPLES
Example 1
A preferable embodiment of the present invention heats a chelate
complex Ni-DMG comprised of a transition metal M comprised of Ni
and two dimethyl glyoxime (DMG) molecules and Ni at 350.degree. C.
and generates Ni nanoparticles carried on carbon particles. The
routine and conditions are as shown below.
3 grams of Ni-DMG (commercial product: 99% Strem Chemicals/Aldrich
ref 13478-93-8) were weighed. Ni-DMG is a powder of particle size
of several 10 .mu.m to 100 .mu.m.
A Pyrex.RTM. glass tube with one closed end and one open end
(length 30 cm, outside diameter 10 mm, inside diameter 8 mm) was
packed with said weighed reagent at its closed end. To ensure
uniform temperature of the sample part, this was covered by
aluminum foil.
The tube was placed in an electric furnace, heated so that the
sample part became 350.degree. C., and held there for 4 hours.
During the heating and holding operation, the open end of the glass
tube was left open to the atmosphere.
After this, the electric furnace was turned off. After 30 minutes,
the glass tube (about 200.degree. C.) was pulled out and the
product was taken out.
The product was comprised of amorphous carbon carrying Ni
nanoparticles.
FIG. 1 shows a TEM (transmission electron microscope) photograph.
The product, as shown in FIG. 1(2), is an assembly of long, thin
fibers. A photograph enlarging part of that (area surrounded by
square of FIG. 1(2)) is given in FIG. 1(1). The bright gray parts
(C) show amorphous carbon particles, while the black parts (Ni)
show Ni nanoparticles. The particles have a size, in the example
shown in the photograph, of about 12 nm and are overall 10 to 15
nm.
As a result of analysis by EDX (energy dispersion type X-ray
analysis) and TGA (thermal gravimetric analysis), the product as a
whole had a composition of, at at %, 70% Ni-24% C-6% N.
The specific surface area was 47 m.sup.2/g (measured by "Autosorb"
made by Quantachrome).
The hydrogen storage amount at room temperature and 300 MPa was
0.13 mass % (measured by PCT system of Suzuki Shokan PCT. The
standard was the total mass of the measurement sample.)
Example 2
According to a more preferable embodiment of the present invention,
a mixture of the chelate complex Ni-DMG and alumina of Example 1
was heated to 350.degree. C. to generate Ni nanoparticles carried
on alumina particles. The routine and conditions are as shown
below.
1 gram of alumina whiskers (commercial product: Sigma Aldrich ref.
551-643) was weighed. This was packed together with four alumina
balls in a balling mill container, then 2 g of said Ni-DMG was
added. The result was milled at a rotational speed of 350 rpm for
30 minutes.
The obtained mixed powder was heated by the same routine and
conditions as in Example 1.
The product was generated in the state with the Ni nanoparticles
carried on the alumina whiskers.
FIG. 2 shows a TEM photograph. The bright gray parts indicate
alumina, while the black parts indicate Ni nanoparticles. The
particles had a size of 6 nm in the example shown in the photograph
and were overall 5 to 10 nm.
As a result of analysis by EDX and TGA, the product as a whole had
a composition of, at at %, 67% Ni-7% Al-3% O-16% C-7% Si. Si was
due to some sort of contamination.
The same procedure was followed as in Example 1 to measure the
characteristics. As a result, the specific surface area was 207
m.sup.2/g and the hydrogen storage amount (room temperature and 300
MPa) was 0.33 mass %.
Compared with Example 1, due to the addition of alumina, the
specific surface area was increased 4.4-fold and the hydrogen
storage amount was increased 2.5-fold.
<Effects of Heating Temperature>
Ni-DMG/alumina mixed powder the same as Example 2 was used and heat
treated while changing the heating temperature in various was in
the range of 250 to 450.degree. C. The change in specific surface
area of the product obtained with respect to the heating
temperature is shown in FIG. 3.
As shown in the figure, when heating in the temperature range of
the present invention, that is, 300 to 400.degree. C., a remarkable
increase in the specific surface area was recognized. As explained
above, with heating at a temperature lower than 300.degree. C., the
expected reaction does not occur, while with heating at a
temperature higher than 400.degree. C., there was remarkable
aggregation of particles. In both cases, the desired nanoparticles
could not be obtained. Therefore, the heating temperature of the
present invention is limited to the range of 300 to 400.degree. C.
350.degree. C..+-.30.degree. C. is particular preferable.
FIG. 3 shows the results in the case of using a mixed powder
comprised of Ni-DMG plus alumina as shown in Example 2 as a
starting material, but the relationship between the heating
temperature and the specific surface area of the product was
similar even in the case like in Example 1 of using only Ni-DMG no
addition of alumina) as the starting material. However, the
absolute value of the specific surface area is large when adding
alumina, so the trend in the change with respect to the heating
temperature becomes clearer, so the results in this case are shown
as a typical example in FIG. 3.
<Comparison with Comparative Material>
The Ni nanoparticles obtained in Example 1 and Example 2 and the
conventional bulk Ni particles (specific surface area of less than
1 m.sup.2/g, particle size on order of .mu.m) were measured for
hydrogen storage amount at room temperature while changing the
pressure in the range of 0 to 30 MPa (measurement method similar in
Examples 1, 2). The results are shown together in FIG. 4.
As shown in the figure, with conventional bulk Ni particles, there
was substantially no hydrogen storage (hydrogen storage amount
about 0 ass %). As opposed to this, it was learned that the Ni
nanoparticles generated from Example 1 (starting material: Ni-DMG
alone) and Example 2 (starting material: Ni-DMG+alumina) of the
present invention exhibits an extremely large hydrogen storage
amount. In particular, the hydrogen storage amount was remarkably
improved in the case of Example 2 (starting material:
Ni-DMG+alumina).
In this way, according to the method of the present invention, it
becomes possible to obtain a transition metal such as Ni alone as
nanoparticles.
Further, by adding carrier particles like alumina, metal
nanoparticles having a larger specific surface area can be
obtained. The reasons are believed to be as follows.
Ni particles inherently become small in size. The following two
points are considered as the reasons why the particles become
smaller in size.
First, the size of metal particles at the time of generation may
depend on the strength of the interaction between the carrier and
metal. If the bonding force between alumina and Ni is greater than
the bonding force between carbon and Ni, the restraining force on
aggregation of Ni becomes larger, so the size of the secondary
particles due to aggregation is probably kept small.
Second, it is deduced that the interaction between the carrier and
Ni becomes stronger at the grain boundaries of the carrier. There
is a possibility of the Ni particles preferentially aggregating at
the carrier grain boundaries. If this model matches with the
experimental data, it means that the amount of grain boundaries of
carbon is greater than the amount of grain boundaries of alumina.
The size of the primary particles is smaller in the case of alumina
(2 to 4 nm) than carbon (several 10 s to 100 .mu.m or so), but if
observed by TEM after heat treatment, the alumina whiskers appear
to be larger than the carbon. During heat treatment, the alumina
whiskers aggregate and the effect of the grain boundaries is
reduced.
While just a guess, the experimental fact that the specific surface
area becomes larger and the hydrogen storage amount remarkably
increases in the case of an alumina carrier as compared with a
carbon carrier is either due to the above two mechanisms or due to
other mechanisms. This is a matter for future study.
INDUSTRIAL APPLICABILITY
According to the present invention, there is provided a method of
stably producing nanoparticles of a metal alone, in particular a
transition metal alone.
* * * * *